Today wireless communication systems are mainly used for human-centered communication and services. A trend is, however, to use wireless communication systems for communication and services mainly involving machines. This kind of communication and services are often referred to as Machine-to-Machine (M2M) communication.
Certain types of communication and services within M2M communication are expected to require that a wireless connection, provided by the wireless communication systems, is highly reliable. The wireless connection is required to be highly reliable both in terms of loss of the wireless connection and the possibility of establishing the wireless connection. In the following, the term “reliable” is used in this context. Therefore, for the above mentioned certain types of communication and services within M2M communication, a high reliability of the connection, or the possibility to establish connection, may be said to be required.
This kind of high reliability may also be required for Person-to-Machine (P2M), Person-to-Person (P2P) and Machine-to-Person (M2P) communication.
Services that may need this kind of high reliability include industrial process control services, services for alarm monitoring, services in smart grid applications, control and management of business and/or mission critical processes or services, services for monitoring critical infrastructure and services towards responders in the national security and public safety segment and other similar services.
Furthermore, high reliability for certain services may be beneficial where deployment of nodes, such as radio base station, radio network controller etc., is particularly costly. At the same time, it is desired to achieve sufficient capacity, e.g. in terms of number of connected devices, and/or coverage for the services.
Consider for example a device, such as smart meters for a smart grid, a metering, sensing or activation device, that is deployed in a network at a remote location at high cost. If there would be a failure in communication with such a device e.g. due to bad coverage and/or insufficient capacity, a manual restoration of the communication with the device or a replacement of the device with another device would be required to compensate for the failure. Such compensation may imply high labor costs, which would scale in an unacceptable manner when there are a great number of devices which often is the case in application of M2M communication.
It is known to provide connectivity for M2M devices in a number of different ways using e.g. wired or wireless connections. The wired connections may be copper wires, optical fibers, Ethernet cables or the like. The wireless connections may be provided by use of various Radio Access Technologies (RATs), such as Wi-Fi, Evolved Universal Terrestrial Radio Access Network for Long Term Evolution (EUTRAN/LTE), Universal Terrestrial Radio Access Network for High Speed Packet Access (UTRAN/HSPA), Global System for Mobile communication (GSM) for Enhanced Data GSM Environment (EDGE) Radio Access Network (GERAN) and the like. Moreover, evolutions of the aforementioned RATs as well as other Third Generation Partnership Project (3GPP) networks may be used to provide the wireless connection.
During planning of the radio access networks and/or telecommunication systems mentioned above, it is sometimes desired to set up the radio access network such as to provide a high reliability for M2M devices. High connectivity could then be provided in the following ways.
For example, the radio access network could be deployed as over-dimensioned in terms of transport and/or radio link resources. Over-dimensioning of transport resources may refer to use of optical fibers for communication from a base station, while a peak bit-rate from the base station is 800 Megabits per second and an optical fiber may handle tenth of Gigabits per second. Over-dimensioning of radio link resources refers to deployment of more base stations, antennas, use of more frequency bands, etc. than needed according to an estimated network load. The RAN is said to be over-dimensioned when it is deployed to be able to handle a worst case scenario while still having resources that are available for any upcoming communication.
As another example, so called node availability may be increased by introducing redundancy in a node by installing multiple power units for powering of the node. The node availability may relate to availability of e.g. transport nodes, radio nodes and server nodes, which communicate with the M2M device or control or support the network operation. Node availability decreases on failure of a node, which typically happens when power units for powering of the node breaks down.
As a further example, in some specific network segments, multiple paths could be introduced to avoid single point of failure. An optical fiber ring is able to cope with interruptions of one optical link by routing information in the opposite direction as compared to where the interrupted optical link is located.
In a known wireless network, a monitoring procedure to monitor that a wireless connection is working properly is performed as follows. The wireless network comprises a first network device and a second network device which are inter-connected by a wireless connection.
Hence, in order to check that the wireless connection is working properly, the first network device sends so called heart-beat messages to the second network device. The heart-beat messages are sent from a service executing in the first network device. The wireless connection is said to work properly when the wireless connection fulfills certain requirements relating to the service. The certain requirements are as an example given by a so called Quality Class Indicator which is known from 3GPP Technical Specification (TS) 23.401, section 4.7, and TS 23.203, e.g. Table 6.1.7, which gives standardized QCI values.
In response to a heart-beat message, received at the second network device, the second network device sends a response message. When the first network device receives the response message, the first network device may conclude that the wireless connection is not broken. This means that the first network device concludes that the wireless connection is broken when a time period from the sending of the heart-beat message to the reception of the response message is above a threshold value. At deployment of the wireless network, a configuration of the monitoring procedure, such as periodicity of heart-beat messages sent, the threshold value etc., is determined.
With another monitoring procedure in the same known wireless network as above, the first network device sends so called probe messages. In contrast to the heart-beat message, probe messages are typically sent unconditionally from the first network device. At deployment of the wireless network, the second network device is configured with information about the probe messages sent by the first network device. The information about the probe message may include timing information about when the probe messages are sent and the like. The information about the probe message may be sent to the second network device by means of a suitable configuration message, which carries said information about the probe messages. In this case, the second network node is able to detect that the wireless connection is broken without any need for response message as in the example above. The second network device may detect the broken wireless connection by registering one or more missing, i.e. not received by the second network device, probe messages, since the second network device expects to receive probe messages according to the configuration applied at deployment.
A problem with the known wireless network may be that the applied configuration of the monitoring procedures mentioned above may sometimes not be efficient.